Analysis of local shrinkage patterns of self-adhering and flowable composites using 3D digital image correlation

OBJECTIVE

To analyze local shrinkage patterns in terms of surface shrinkage strains and z-axis displacements in a novel self-adhering composite and a conventional flowable composite using three-dimensional digital image correlation.

METHOD AND MATERIALS

Seven samples of each material were prepared in cylindrical Teflon molds 5 mm in diameter and 2 mm thick. The surface of the composites facing the cameras was sprayed with a fine layer of black paint. The unsprayed surface of each sample, opposite the one facing the cameras, was light cured for 40 seconds using a light-emitting diode unit. Digital images were taken immediately before and after light curing. Shrinkage was calculated as von Mises strains, and z-axis displacements were measured in microns. The data were statistically analyzed using two-way ANOVA at a = .05.

RESULTS

No significant difference in strain was observed between the two materials (P > .05). Strain distribution was nonhomogenous--the outer segments showed significantly higher strains than central parts in each material (P < .05). The opposite was observed for z-axis displacements-significantly greater displacements were found in central parts compared to the outer segments (P < .05).

CONCLUSION

Different shrinkage vectors across the surface of the tested flowable composites showed predominant in-plane shrinkage of the outer surface segments and out-of-plane shrinkage of the inner segments. These complex local deformation patterns in composite materials indicate zones of different types of forces exerted on the tooth-restoration interface in situ.

Psychotropic medication use in children and adolescents in an inpatient setting

Medication can be an effective part of treatment for several psychiatric disorders of childhood and adolescence but its use should be based on a comprehensive psychiatric evaluation and treatment plan. The aim of this study was to evaluate psychotropic medication use for children and adolescents treated as inpatients and to compare it with principles of rational pharmacotherapy, thus identifying possible downsides of current practices and pointing a way towards safer and more efficient practices. This is a descriptive study of prescribing trends at the Clinical Department for Children and Adolescents of the Institute of Mental Health in Belgrade, during the period from September 2009 to September 2010. Analyzed demographic data (age, gender) and the number of hospitalizations were obtained from medical histories, while diagnoses were obtained from discharge notes. Prescribed therapy was copied from medication charts. Drug dosages were analyzed as average daily doses prescribed during the hospitalization. Psychiatric diagnoses were classified according to The International Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). During the examined time period, 264 patients were hospitalized (61.4% males), with an average age of 11.4±5.1 years. We have found that 66.3% of admitted patients were treated with pharmacotherapy in addition to other treatment modalities. There was a highly significant correlation between the age of patients and the prescribed dosage (Spearman's rho=0.360, p<0.001) as well as the number of prescribed drugs (Spearman's rho=0.405, p<0.001). The most commonly diagnosed psychiatric disorders were: autism spectrum disorders (20.8%), conduct disorders(19.7%), mixed developmental disorder (14.8%), adjustment disorder (7.2%), mental retardation (7.2%),acute psychosis (4.5%), and ADHD (2.3%). The most commonly prescribed medications were antipsychotics(45.9%), followed by antidepressants (17.2%), mood stabilizers (16.1%), benzodiazepines (14.4%), and other psychotropic drugs (6.4%). The most commonly prescribed antipsychotic was risperidone, used for more than 50% of the patients treated with antipsychotics. Taken together risperidone and chlorpromazine were more than 75% of all prescribed antipsychotics. 98.4% of prescribed antidepressants belonged to the SSRIs,with sertraline and fluoxetine accounting for almost 90% of them. All prescribed dosages were in accordance with the official guidelines. This is the first survey in Serbia to document the practice of prescribing psychotropic medication in the field of child and adolescent psychiatry. Current drug-prescribing practices at the Clinical Department for Children and Adolescents of the Institute of Mental Health in Belgrade are in accordance with current practices in the United States and Europe. Not every child with symptoms of mental health problems needs pharmacological treatment; when they do, the general rule of thumb should be "start low, go slow, and taper slowly". Follow-up studies are necessary to assess the change of trends, as well as studies in different patient populations and health centers, in order to globally evaluate psychotropic medication use in children and adolescents in Serbia.

Clinical reproducibility of three electronic apex locators

AIM

To compare the reproducibility of three electronic apex locators (EALs), Dentaport ZX, RomiApex A-15 and Raypex 5, under clinical conditions.

METHODOLOGY

Forty-eight root canals of incisors, canines and premolars with or without radiographically confirmed periapical lesions required root canal treatment in 42 patients. In each root canal, all three EALs were used to determine the working length (WL) that was defined as the zero reading and indicated by 'Apex', '0.0' or 'red square' markings on the EAL display. A new K-file of the same size was used for each measurement. The file length was fixed with a rubber stop and measured to an accuracy of 0.01 mm. Measurements were undertaken by two calibrated operators. Differences in zero readings between the three EALs in the same root canal were statistically analysed using paired t-tests with the Bonferroni correction, Bland-Altman plot and Linn's concordance correlation coefficients at α = 0.05.

RESULTS

Mean and standard deviation values measured by the three EALs showed no statistically significant differences. Identical readings by all three EALs were found in 10.4% of root canals. Forty-three per cent of readings differed by less than ± 0.5 mm and 31.3% exceeded a difference of ± 1 mm.

CONCLUSIONS

The clinical reproducibility of Dentaport ZX, RomiApex A-15 and Raypex 5 was confirmed with the majority of readings within the ± 1.0 mm range. However, the small number of identical zero readings suggests that EALs are not reliable as the sole means of WL determination under clinical conditions.

Micro-raman assessment of the ratio of carbon-carbon double bonds of two adhesive systems cured with LED or halogen light-curing units

PURPOSE

the purpose of the study was to compare the ratio of carbon-carbon double bonds (RDB) of two adhesive systems cured by five different light-curing units (LCUs) using micro-Raman spectroscopy. materials and methods: ten samples of an etch-and-rinse (Excite), a two-step self-etching adhesive system (AdheSE) - ie, primer and bond mixed - and AdheSE Bond only were prepared and cured with one of the following LEDs: Elipar Freelight2; Bluephase; SmartLite; Coltolux, each for 10 s; or a conventional halogen Prismetics Lite for 10 s or 20 s. Micro-Raman spectra were obtained from uncured and cured samples of all three groups to calculate the RDB. Data were statistically analyzed using ANOVA.

RESULTS

the mean RDB values were 62% to 76% (Excite), 36% to 50% (AdheSE Primer+Bond) and 58% to 63% (AdheSE Bond). At 20 s, Prismetics Lite produced significantly higher RDB in Excite than the other LCUs and Prismetics Lite at 10 s (p < 0.05). Prismetics Lite at 20 s and Elipar produced comparable RDB values of AdheSE Bond and AdheSE Primer+Bond (p > 0.05). Excite showed significantly higher RDB values than AdheSE (p < 0.05) whilst AdheSE Bond showed significantly higher RDB than AdheSE Primer+Bond (p < 0.05).

CONCLUSION

the etch-and-rinse adhesive cured with the halogen LCU for 20 s gave higher conversion than LED LCUs or halogen for 10 s curing time. The highest intensity LED [Elipar] produced higher or comparable conversion compared to the lower intensity LED LCUs for the same curing time. The etch-and-rinse adhesive showed higher RDB than the self-etching adhesive system. The presence of the primer in the self-etching adhesive compromised polymerisation.

Quantification of monomer elution and carbon-carbon double bonds in dental adhesive systems using HPLC and micro-Raman spectroscopy

OBJECTIVES

To quantify monomer elution from different adhesive systems using reverse-phase high-performance liquid chromatography (HPLC) and correlate this elution with the ratio of carbon-carbon double bonds from monomer to polymer (RDB) obtained using micro-Raman spectroscopy.

METHODS

Thirty dentine discs were cut from 30 human, intact, third molars and randomly allocated to five groups according to the adhesive applied: total-etch, Excite (Ivoclar Vivadent), two-bottle self-etch, Clearfil SE (Kuraray), one-bottle self-etch, Clearfil 3S (Kuraray), ormocer-based, Admira (Voco) and Filtek Silorane adhesive system (FS) (3M ESPE). Monomer elution was studied 1h, 6h, 24h, 96h and 7 days after immersion in 75% ethanol/water. The RDB was calculated immediately after light-curing and thereafter at 24h and 7 days. The data were statistically analysed using one-way ANOVA and Pearson's correlation coefficient (p<0.05).

RESULTS

More than 90% of the whole elution occurred during the first 1h, except for BisGMA in FS, with the highest absolute amount from Clearfil SE and the highest wt% from Admira. Initial RDB was in the ascending order FS<Admira<Excite<Clearfil SE<Clearfil 3S. In all groups, the RDB was significantly higher after 24h and 7 days than immediately after light-curing (p<0.05). Negative correlation was found only for the elution of HEMA and the RDB of Clearfil 3S.

CONCLUSIONS

Different adhesive systems showed different monomer elution kinetics. In all systems, the RDB increased after monomer elution. Overall, no direct correlation exists between the RDB of adhesives and the elution of unreacted monomers.

Temperature rise within the pulp chamber during composite resin polymerisation using three different light sources

The purpose of the study was to compare temperature rise during polymerisation of resin based composites (RBCs) with two LED light curing units (LCUs) compared to a halogen control light.

A study of temperature rise in the pulp chamber during composite polymerization with different light-curing units

AIM

The study compared pulp temperature rise during polymerization of resin-based composites (RBCs) using halogen and LED light-curing units (LCUs).

METHODS AND MATERIALS

A total of 32 teeth extracted from patients aged 11-18 years were used in the study. Thermocouples placed on the roof of the pulp chamber using a novel 'split-tooth' method. In Group 1 a halogen LCU with a light intensity of 450 mW cm(-2) was used and in Group 2, an LED LCU with a light intensity of 1100 mW cm(-2) was used. The teeth were placed in a water bath with the temperature regulated until both the pulp temperature and the ambient temperature were stable at 37 degrees C. Continuous temperature records were made via a data logger and computer. The increase in temperature from baseline to maximum was calculated for each specimen during the curing of both the bonding agent and the RBC.

RESULTS

The rise in pulp temperature was significantly higher with the LED LCU than with the halogen LCU for bonding and RBC curing (p<0.05). The major rise in temperature occurred during the curing of the bonding agent. During the curing of the RBC, rises were smaller.

CONCLUSIONS

Curing of bonding agents should be done with low intensity light and high intensity used only for curing RBC regardless of whether LED or halogen LCUs are used.

Changes in post-tetanic potentiation of A-fiber dorsal horn field potentials parallel the development and disappearance of neuropathic pain after sciatic nerve ligation in rats

Significant plastic changes in spinal nociceptive processing appear to accompany peripheral nerve injury or inflammation. Using a well-established model of neuropathic pain, we have recently reported that loose ligation of the sciatic nerve was accompanied by a long-lasting post-tetanic potentiation of sciatic-evoked A-fiber superficial dorsal horn field potentials. In the present study we demonstrate that the typical disappearance of thermal hyperalgesia as a behavioral sign of neuropathic pain several weeks after loose sciatic nerve ligation is accompanied by the loss of the long-lasting potentiation. These data suggest that a significant but reversible shift in the processing of sensory information in the spinal dorsal horn follows peripheral nerve injury, and lend further support to the notion that long-lasting synaptic plasticity may contribute to the development of neuropathic pain.

Contribution of GABA-A receptors to metaplasticity in the spinal dorsal horn

Metaplasticity is a higher-order form of synaptic plasticity that is induced by synaptic or cellular activity, which by itself may not produce changes in synaptic strength, but which modifies subsequent changes in synaptic efficacy. In this description of metaplasticity in the spinal dorsal horn, we report that a 50 Hz high-frequency tetanus, previously shown to elicit a potentiation of sciatic-evoked A-fiber spinal dorsal horn potentials, caused a depression when coupled with a more rapid rate of repetitive stimulation. This depression appeared to be dependent upon GABA(A) receptor activation because the 50 Hz tetanus elicited a persistent potentiation when the GABA(A) antagonist bicuculline was injected at 1 mg/kg (but not at 0.5 mg/kg) prior to tetanic stimulation. These data suggest the presence of strong inhibitory inputs in the spinal dorsal horn that are activated by an increased rate of primary afferent firing. The activation of these inputs may be necessary to prevent prolonged bursts of afferent activity from modifying synaptic strength because the latter may contribute to the development of persistent pain following peripheral nerve injury.

Increased spinal monoamine concentrations after chronic thoracic dorsal rhizotomy in goats

In goats, bilateral thoracic dorsal rhizotomy (TDR) causes severe ventilatory failure during exercise, followed by progressive functional recovery. We investigated spinal neurochemical changes associated with TDR and/or functional recovery by measuring spinal concentrations of the monoamines serotonin (5-HT), norepinephrine, and dopamine via HPLC. Changes in 5-HT and calcitonin gene-related peptide were visualized with immunohistochemistry. Goat spinal cords were compared 4-15 mo after TDR from T(2) to T(12) (n = 7) with sham-operated (n = 4) or unoperated controls (n = 4). TDR increased the concentration of cervical 5-HT (C(5)-C(6); 122% change), caudal thoracic norepinephrine (T(7)-T(11); 53% change), and rostral thoracic dopamine (T(3)-T(6); 234% change). TDR increased 5-HT-immunoreactive terminal density (dorsal and ventral horns) and nearly eliminated calcitonin gene-related peptide immunoreactivity in the superficial laminae of the dorsal horn in rostral thoracic segments; both effects became less pronounced in caudal thoracic segments. Thus TDR elevates monoamine concentrations in discrete spinal regions, including possible compensatory changes in descending serotonergic inputs to spinal segments not directly affected by TDR (i.e., cervical) but associated with functionally related motor nuclei (i.e., phrenic nucleus).

Differential effects of inorganic lead on hippocampal long-term potentiation in young rats in vivo

Tetanic stimulation at 50 Hz elicited long-term potentiation (LTP) in the hippocampal CA1 region of 28-day-old control animals. In contrast, no significant potentiation was seen following the same tetanus in animals chronically exposed to 1000 ppm of lead acetate during development. Gender differences were observed in animals exposed to 500 ppm of lead. In females, LTP was significantly attenuated, while in males the LTP was identical to that of controls.

Loose ligation of the rat sciatic nerve is accompanied by changes in the subcellular content of protein kinase C beta II and gamma in the spinal dorsal horn

This study examined whether loose ligation of the sciatic nerve was accompanied by specific changes in protein kinase C (PKC) betaII and gamma isozymes in the spinal dorsal horn. The isozyme staining pattern was visualized with immunocytochemistry. Their content in subcellular fractions was estimated from Western immunoblots. In control animals, PKC betaII immunoreactivity extended from lamina I into lamina III, while PKC gamma immunoreactivity was concentrated within laminae II and III. In ligated animals exhibiting thermal hyperalgesia, the content of both PKC betaII and gamma in the synaptosomal membrane fraction, but not crude cytosolic fraction, was significantly greater by an average of 40% from their respective controls. These data support suggestions that peripheral nerve injury engenders plastic changes in the dorsal horn to contribute to the development of persistent pain.

Long-term changes in sciatic-evoked A-fiber dorsal horn field potentials accompany loose ligation of the sciatic nerve in rats

The goal of the present study was to examine whether loose ligation of the sciatic nerve was associated with long-term changes in neuronal excitability in the spinal dorsal horn in urethane-anesthetized rats. The sciatic nerve was stimulated with 0. 1 ms long pulses at 1 stimulus/5 min, and the evoked dorsal horn field potentials remained stable in the absence of tetanic stimulation. In one set of control and ligated animals, high-frequency tetanic stimulation was applied to the nerve at 50 Hz (one 400 ms train of twenty 0.1 ms pulses), and the field potentials were recorded again (1 stimulus/5 min) for up to 4 h post-tetanus. In control animals, this protocol produced significant increases in field potential amplitudes at 15, 30 and 60 min post-tetanus. Interestingly, after this time the evoked field potentials began to decrease, and attained less than 50% of their pre-tetanic values at 240 min post-tetanus. In contrast, in ligated rats the pattern of post-tetanic potentiation was significantly different as the increases in amplitude persisted, and at 240 min post-tetanus the field potentials were almost twice their baseline values. In another set of control and ligated animals, low-frequency tetanic stimulation was applied at 5 Hz (one 400 ms train of two 0.1 ms pulses). Again a differential pattern of post-tetanic responses between control and ligated rats was seen. In control animals, a significant decrease in amplitude was evident within 30 min, and the depression became progressively more pronounced as the field potentials attained about a quarter of their baseline values at 180 min, and remained at these low levels at 240 min post-tetanus. On the other hand, in ligated animals, the depression was not significant, and at 240 min post-tetanus the field potentials were still at about 80% of their baseline values. These data demonstrate that long-term changes in spinal dorsal horn neuronal excitability accompany sciatic ligation to perhaps contribute to the development of neuropathic pain. These changes may result from a lessening of normally strong inhibitory processes in the spinal dorsal horn to generate conditions which favor post-tetanic potentiation over depression of dorsal horn neuronal responses.

Analgesic effects of butorphanol and buprenorphine in conscious African grey parrots (Psittacus erithacus erithacus and Psittacus erithacus timneh)

OBJECTIVE

To evaluate effects of butorphanol tartrate and buprenorphine hydrochloride on withdrawal threshold to a noxious stimulus in conscious African grey parrots.

ANIMALS

29 African grey parrots (Psittacus erithacus erithacus and Psittacus erithacus timneh).

PROCEDURE

Birds were fitted with an electrode on the medial metatarsal region of the right leg, placed into a test box, and allowed to acclimate. An electrical stimulus (range, 0.0 to 1.46 mA) was delivered to each bird's foot through an aluminum perch. A withdrawal response was recorded when the bird lifted its foot from the perch or vigorously flinched its wings. Baseline threshold to a noxious electrical stimulus was determined. Birds then were randomly assigned to receive an i.m. injection of saline (0.9% NaCl) solution, butorphanol (1.0 mg/kg of body weight), or buprenorphine (0.1 mg/kg), and threshold values were determined again.

RESULTS

Butorphanol significantly increased threshold value, but saline solution or buprenorphine did not significantly change threshold values.

CONCLUSIONS AND CLINICAL RELEVANCE

Butorphanol had an analgesic effect, significantly increasing the threshold to electrical stimuli in African grey parrots. Buprenorphine at the dosage used did not change the threshold to electrical stimulus. Butorphanol provided an analgesic response in half of the birds tested. Butorphanol would be expected to provide analgesia to African grey parrots in a clinical setting.

A technique for evaluating analgesia in conscious perching birds

OBJECTIVE

To develop a technique for objective assessment of modulation of nociperception in conscious perching birds.

ANIMALS

31 adult African grey parrots.

PROCEDURE

Birds were randomly assigned to receive saline (0.9% NaCl) solution (n = 10), butorphanol tartrate (11), or buprenorphine hydrochloride (10), i.m. Birds were fitted with a surface electrode on the medial metatarsus of 1 leg. An electrical stimulus was delivered to the bird's foot through an aluminum surface on half of the perch. The alternate side of the perch delivered a noxious thermal stimulus. A withdrawal response to either stimulus was recorded when the bird lifted its foot or vigorously flinched its wings.

RESULTS

Responses to thermal stimuli were extremely variable during baseline testing and after administration of drugs. Thus, significant differences were not detected after drug injection. In contrast, responses to an electrical stimulus were predictable with much less variation.

CONCLUSIONS AND CLINICAL RELEVANCE

This method and device allowed for the reliable determination of withdrawal threshold in perching birds. Use of this technique for objective assessment of modulation of nociperception in conscious perching birds will enable assessment of analgesic drugs.

Chronic exposure to lead acetate affects the development of protein kinase C activity and the distribution of the PKCgamma isozyme in the rat hippocampus

This study has examined the effect of chronic inorganic lead exposure on phospholipid-dependent protein kinase C (PKC) activity, and the distribution of its alpha (alpha), beta II (betaII), gamma (gamma), and zeta (zeta) isozymes in subcellular fractions of the developing rat hippocampus. Dams were exposed to either 0 or 1000 ppm lead acetate in their drinking water for one week and mated. Offspring were exposed to lead in utero, via lactation, and directly in the drinking water after weaning. The offspring were sacrificed at postnatal days 1 (P1), 8 (P8), 15 (P15), and 29 (P29). PKC activity was determined in the post-synaptosomal supernatant (PSS) and synaptosomal (P-2) membrane fractions by an in vitro assay using histone as the phosphate acceptor. The selected PKC isozymes were detected by immunoblotting techniques. In control animals, PKC activity (pmole/min/mg total protein) in both subcellular fractions substantially increased between P1 and P8. In chronically exposed rats exhibiting clinically relevant blood lead concentrations, this marked increase in PKC activity on P8 was significantly attenuated in both subcellular fractions. On this postnatal day, the amount of immunodetectable PKC gamma was significantly higher in the synaptosomal membrane fraction of lead-exposed rats. Other isozymes were unaffected. These results imply that in lead-exposed animals the PKC gamma isozyme was inactive even though it was associated with the membrane. These results also suggest that prolonged exposure to the heavy metal attenuated PKC activity at an important developmental time to potentially adversely affect normal hippocampal function.

Symposium overview: chemical modulation of neuroreceptors and channels via intracellular components

Whereas the roles of G proteins and protein kinases in various neuroreceptors and ion channels have been studied extensively, their roles in the actions of drugs and toxicants on these receptors and channels remain to be elucidated. Almost all drugs and toxicants exert multiple actions on multiple target sites, and there is no reason to assume that a chemical modulates a receptor/channel via a single mechanism. In fact, experimental evidence is slowly but steadily being accumulated to indicate that certain drugs and toxicants modulate neuroreceptor/channel functions through interactions with intracellular components such as G proteins and protein kinases. Multiple actions of a toxicant on various receptors/channels may be explained on the basis of its interaction with the G protein/kinase system that is a common denominator of the target sites. This is a virgin field that promises a quantum leap in the coming years. Each presentation and discussion will focus on expected future developments and potential significance in the field of neurotoxicology.